Muffler



Nov. 25, 1936. A. H. AARON 1,782,396

XUFFLER Filed Jan. 29. 1929 Patented Nov. 25, 1930 PATE FFIQE ARTHUR HARRY AARON, OF AMITYVILLE, NEW YORK, ASSIGNOR TO FAIRCHILD AVIATION CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE MUFFLER Application filed January 29, 1929. Serial No. 335,904.

This invention relates in general to sound mufflers, and more particularly to the construction and the method of assembling a mufier adapted for silencing the exhaust of an internal combustion engine.

A primary object of this invention is to provide a mufiier of light weight and of simple construction which will be efiective as a silencer without creating prejudicial back pressure in the motor to which it is attached.

Another object is to arrange the baiiiing means in such ratio relative to the extent of travel of the exhaust gases and to arrange for a predetermined variance throughout the length of the muflier casing to accomplish the aforementioned primary object.

A further object is to provide a novel method of assembling the baffle means whereby the desired bafiling efi'ect may be obtained.

With the foregoing and other objects in view, the invention resides in the combination of parts and in the detail of construction hereinafter set forth, certain embodiments being set forth in the accompanying drawings in which:

Figure 1 is a longitudinal section through the mutfier casing showing the baflles in perspective.

Figure 2 is a front elevation of a blank plate.

Figure 3 is similar to Figure 2 showing the plate apertured.

Figure 4 is similar to Figure 3 showing the plate apertured and split.

Figure 5 is a perspective of the plate shown in Figure 4, formed into a spiral by stretching the same horizontally.

Referring more particularly to the drawings, the device is shown in Figure l as comprising a casing C of substantially uniform size throughout. Arranged interiorly of the casing are a series of spiral or helical baffles. Baffle S is shown connected in any suitable manner to the casing at 1 while the other end of the baffle S is connected toa second bafiie S at 2 by a suitable method such as welding. Similarly baflie S is connectedto S at 3; S to S at 4; S to S at 5. The number of these baffies is purely a matter of choice.

The novel method of making these baflies is best understood by reference to Figure 2 in which is shown a thin circular metallic blank which, in the process of forming same into a spiral baiiie, is first provided with a central aperture D. Obviously, the process could start with washers if the apertures were of the desired size with respect to the size of the washers. However, the next step is the splitting of the washer from any point on the periphery to the aperture. The sizes of the washer and its aperture are such that the distance of the split E as represented from the point A to B is approximately one third of the effective diameter of the washer.

The two ends of the washer thus formed are pulled in opposite longitudinal directions to form a spiral as shown in the last step of Figure 2.

The problem to be solved in eifective and efficient engine mufllers is to avoid the creation of prejudicial back pressure while attempting to silence the sound accompanying the discharge of the engine exhaust. A further problem in the provision of a muflier suitable for aeronautical engines, which type the present invention is more particularly concerned, is to reduce the assembly to the minimum weight.

As an example of actual construction for a mufiler for a particular engine of predetermined horse power and number of cylinders, I have actually employed a mufiler having such dimensions that the bailie S nearest to the inlet end of the casing C will be ten inches long; S nine inches; S eight inches; S, seven inches; and 8, six inches. Thus the pitch of baflie S will be the greatest and each succeeding baffle correspondingly progressively smaller. Obviously, therefore, the speed of travel of the exhaust gases through the extent of bafiie S will be comparatively great and will be correspondingly progressively less in their travel throughout the succeeding bafiies. 4

The spiral bafiie is the best effective manner in silencingthe discharge of gases by relatively accelerating the flow of gases due to the whirling motion imparted thereto to such a degree as to definitely eliminate abrupt retardation, the consequent creation of back pressure and its well known attendant harmful effects on the operation of the engine. The series of bafies shown and described herein, however, are designed after a careful study of the characteristics of the particular engine used in such a manner as to properly regulate the rate of flow of exhaust gases, and varying in steps the rate of flow at periodic intervals for such duration as provided for in the construction described.

This provides for a comparatively rapid rate of discharge through a casing of relatively small diameter, of peripherally whirl'- ing exhaust gases and the resulting elimination of sound without creating back pressure. Furthermore, these whirling gases travelling relatively rapidly, will blend perfectly with and surround such gases passing directly through the bafile apertures in such a manner as to prevent a sharp vacuum and attending sound due to replacement of suddenly displaced air.

The simple method of making the bafies to specification renders the'mufier most easily and cheaply manufactured or adjusted to meet conditions over a wide range.

It is to be understood that various changes in the construction of the embodiment illustrated in the drawings may be made without departing from the spirit of the invention and it is not desired to limit the invention to this illustration but to interpret the invention broadly in light of the appended claims.

I claim:

1. In a muifier, a casing, bafiing means of a substantially spiral form and of a pitch successively lessened in predetermined degrees at predetermined points throughout its length toward the outlet of said casing.

2. In a mufiler, a casing, bafliing means having a centrally disposed aperture, said means being of a substantially spiral form and of a pitch successively lessened in predetermined degrees at predetermined points throughout its length toward the outlet of said casing.

3. In a muflier, a casing, a series of bafies of substantially spiral form, each of said bafiies having a different but uniform pitch, thev bafiie having the largest pitch being arranged adjacent the inlet of said casing and the remainder of said bafiles being arranged in corresponding order with respect to their degree of pitch.

4. In a mufier, a casing, a series of baflles of substantially spiral form, each of said baflies having a diflerent but uniform pitch, the baflie having the largest pitch being arranged adjacent the inlet of said casing and the remainder of said bafies being arranged in corresponding order with respect to their degree of pitch, said baffles having registering centrally disposed apertures.

5. In a mufller, a casing, a series of bailies of substantially spiral form, each of said bafies having a different but uniform pitch, the battle having the largest pitch being arranged adjacent the inlet of said casing and the remainder of said haflies being arranged in corresponding order with respect to their degree of pitch, said bafiies having their ends connected to form a continuous spiral, and said bafiies having registering centrally disposed apertures.

6. In a mufier, a casing of uniform size throughout, a series of substantially spiral shaped bafies of different length and of different but uniform pitch, the bafile of greatest length and correspondingly the greatest pitch being arranged adjacent the inlet of the casing, the remainder of said bafies being arranged in correspohding order with respect to their length and corresponding degree of pitch.

7 In the manufacture of a mufier having a casing and a series of substantially helical shaped baflling members, the method. of mak ing and assembling said baifies which consists in centrally aperturing a series of flat plates of the same diameter, splitting each plate from one point on its periphery to the aperture, pulling the ends thus formed in opposite directions to a predetermined degree to form a helix comprising a series of convolutions of predetermined length and pitch, the similar forming of a series of helices of length and pitch correspondingly successively less in predetermined degree, and the arrangement of said helical bafie elements in said casin in corresponding relation with respect to t e inlet of said casing.

8. In the manufacture of a mugfiier having a casing and a series of substantially helical shaped bafliing members, the method of making and assembling said baflies which consists in centrally aperturing a series of flat plates of the same diameter, splitting each plate from one point on its periphery to the aperture, pulling the ends thus formed in opposite directions to a redetermined degree to form a helix comprising a series of convolutions of predetermined length and pitch, the

similar forming of a series of helices of length and pitch correspondingly successive ly less in predetermined degree, the attaching of the corresponding ends of said helical bafiie elements and the arrangement thereof to provide a registry of said centrally disposed apertures.

9. In a mufier, a series of stationary helical bafie plates arranged within a casing, each of said bafie plates being formed to constitute a series of convolutions of a uniform pitch, and forming in itself a continuous helical baflle element of uniform pitch throughout, all of said helical baflle elements being of a difierent length and pitch and arranged within said casing, and attached to each other in the order of decreasing length In testimony whereof, I have signed my name to this specification this 25th day of January, 1929.

ARTHUR HARRY AARON. 

